In an image forming apparatus such as a copying machine, a printer or the like, a sheet is nipped and transported to a transfer position after a front end position of the sheet transported from a sheet feeder is aligned by a registration roller pair. In the registration roller pair, there is a device that rotates both rollers that nip the sheet therebetween at the same circumferential speed for the purpose of preventing the sheet from slanting to prevent a positional displacement of a transfer image on the sheet.
However, if outer diameters of the rollers are varied due to abrasion while the registration roller pair rotates, there is a risk that slanting or transport delay of the sheet occurs due to a difference in the circumferential speed between both the rollers, and a trouble of an image caused by transfer displacement occurs.
For that reason, the development of the registration rollers that are maintained at the same circumferential speed even if the rollers are abraded is desired.